Avoid unnecessary multiline parentheses

[Morriar]

Avoid unnecessary parentheses when autocorrecting multiline T.must calls without comments.

Before:

variant = (
  InventoryItemVariant.preload(:variant).where(inventory_item_id: @inventory_item_id).first!.variant
).not_nil!

After:

variant = InventoryItemVariant.preload(:variant).where(inventory_item_id: @inventory_item_id).first!.variant.not_nil!

Calls containing comments keep the grouped form so comments and internal indentation are preserved.